CamScanner: Feartan agus Taic

DNA Structure and Replication

• DNA is the molecule that stores genetic information for all organisms.
• DNA is heritable, meaning it is passed from parent to offspring.
• Early biologists understood that traits were heritable, but not the exact mechanism.
• DNA's structure and role in heredity was gradually discovered.
• Technology advancements allowed scientists to understand DNA better.
• DNA's appearance is complex, with images showing it at multiple levels of detail.

DNA Codes for Proteins

• DNA (deoxyribonucleic acid) stores genetic instructions.
• DNA builds proteins.
• RNA (ribonucleic acid) acts as an intermediary linking DNA to proteins.
• The central dogma of molecular biology explains the flow of information.
• Proteins have diverse roles (enzymes, structural support, transport).
• Proper DNA structure is crucial for building functional proteins, including motor proteins like kinesin.

Griffith's Experiments

• Griffith investigated pneumonia-causing bacteria (types S and R).
• When heat-killed S bacteria mixed with live R bacteria, live S bacteria were found in the mice.
• He called this transferring principle, indicating a molecule transforming R bacteria into S.

Avery's Experiments

• Avery investigated Griffith's transforming principle.
• Avery and others identified DNA as the transforming principle.
• They conducted enzyme tests and found that destroying DNA stopped the transformation.
• They concluded DNA was the genetic material.

Hershey and Chase Experiments

• These experiments provided further confirming evidence that DNA was the genetic material.
• Bacteria were infected with bacteriophages (viruses that infect bacteria).
• The phages' DNA contained radioactive phosphorus (only DNA contains phosphorus).
• Their results showed radioactivity in the bacteria, confirming DNA carried genetic information.

DNA Structure

• DNA is a long polymer of repeating subunits called nucleotides.
• Nucleotides differ by their nitrogenous bases (cytidine, thymine, adenine, guanine).
• Purines (adenine and guanine) have a double-ring structure.
• Pyrimidines (cytosine and thymine) have a single-ring structure.

Chargaff's Experiments

• Chargaff determined the base pairings in DNA.
• The amounts of adenine and thymine are equal, and the amounts of cytosine and guanine are equal.
• The ratios of these bases vary between species.

Franklin's X-ray Crystallography

• Franklin's X-ray images revealed DNA's helical structure.
• The photographs of DNA showed an X pattern characteristic of a helix.

Watson and Crick's Model

• Watson and Crick used Franklin's data to propose a double-helix model of DNA.
• The double-helix structure shows two strands of DNA twisted around each other.
• Nitrogenous bases are paired in the centre (A with T and G with C), and the deoxyribose and phosphate structures are on the outside of the structure.
• Bases are paired based on specific shapes and size requirements.

DNA Replication

• DNA copies itself during the S phase of the cell cycle.
• An enzyme called helicase separates the DNA strands.
• Free nucleotides are paired with template strands.
• DNA polymerase joins the new nucleotides.
• The result is two identical DNA molecules that are exact copies of the original.
• This process is called semiconservative replication.

Protein Synthesis

• Transcription is the copying of a DNA sequence into RNA.
• RNA polymerase is involved in transcription.
• Translation is the conversion of RNA to a polypeptide.
• Ribosomes are the site of translation.
• mRNA, rRNA, and tRNA play essential roles in translation.

Mutations and Proteins

• A mutation is a change in the sequence of nucleotides.
• Point mutations replace one nucleotide with another.
• Frameshift mutations insert or remove nucleotides, altering the reading frame
• Mutations affect the protein's structure, which may consequently affect its function, potentially causing effects like sickle cell anemia.

Synthetic Cells

• Scientists created synthetic cells by inserting a complete genome into a new cell.
• Researchers studying synthetic cells aim to learn how minimal genetic material is needed for life.

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